The present invention is directed generally to a data transmission network and more particularly to such a network wherein each of the multiple receivers are assigned an address indicative of multiple characteristics of the owner of the receiver and wherein each receiver is operative to receive and store in random access memory (RAM) those messages which have an address corresponding to any one of the multiple characteristics designated by the receiver address, the receiver furthermore being operative to signal the operator when a message has been stored.
Many systems have been devised for transmitting and receiving data, however, all of these devices have certain shortcomings. Facsimile machines and computer modems can transmit and receive data over telephone lines but the required physical hardware link limits their usefulness.
Radio teletype systems have been known for many years. Data is transmitted without an address and without error-checking protocols. Accordingly, radio teletype owners are without a means of screening messages having no relevance to them.
Within the Amateur Radio Service, an operator can send a digital message throughout a region and receive an acknowledgement. However, these messages may only be sent to a single other operator or electronic bulletin board (Packet Radio is the descriptive title of the mode of communication which refers to this message passing).
Known to the art are communications systems that utilize electromagnetic radiation to send information not available to the public at large. Systems of this type include the Physician's Radio Network, and stock and commodity price data services which transmit quotations and prices with ebsidic code over sub-audible carriers in the regular FM broadcast band. The Physician's Radio Network provides physicians with a receiver that receives audio on a sub-audible carrier in the FM broadcast band. However, messages important to a given listener are only heard if the listener is present at the time of the broadcast.
Many professionals use pagers which receive audio or digital data communications meant only for their pager. This audio or digital data is received after an alert, such as a tone which causes the squelch to be broken and turn on the pager.
Burke, et al. U.S. Pat. No. 4,636,791 discloses a two-way radio system which enables remotes to be addressed in a manner to alert selected classifications of remote operators to respond to the alert code from a master station. However, the addressing capability is limited in that the address encoded alert code is not operative to convey a lengthy message. The Burke, et al. device simply alerts the remote operators to establish two-way voice communications.
Mori, et al., European Patent 0 136 677 discloses a paging receiver improvement for decreasing the number of switches necessary for processing stored messages. Mori, et al. does not teach a method of addressing a single message to a plurality of receivers ("group calling").
Both Giallanza, et al., U.S. Pat. No. 4,383,257, and Morrien, et al., PHILIPS TELECOMMUNICATION REVIEW, Vol. 36, No. 1, April 1978describe devices with group calling capabilities. However, these devices are incapable, if not inoperative, for quickly and inexpensively sending a single message to receivers having an address indicating they are of a class interested in the content of a particular message.
Accordingly, a primary object of the invention is to provide an improved data transmission network.
Another object of the invention is to provide such a network wherein a message transmitted to multiple receivers may be encoded with an address designating one or more selected classifications of receivers so that a particular receiver will receive and store only relevant messages.
Another object is to provide such a network wherein the receivers are operative to receive and store messages even when unattended by an operator.
Another object of the invention is to provide such a network having a large capacity memory which is not constrained to receiving only messages of limited length.
Another object is to provide such a network that may be established using existing technology and economical instrumentation.
Another object of the invention is to provide such a network which is simple, economical and efficient in operation.